Serological and immunochemical studies of H-2 allospecificities on K36, a syngeneic tumour of AKR.

Expression of H-2 antigenic specificities on K36, a spontaneous leukaemia originating from AKR (H-2k) mice, was studied by serology and immunochemistry. Two ascites lines of the tumour, as well as a tissue culture adjusted and cloned tumour line, were used in these studies with similar results being obtained. K36 expresses on its cell surface D-region encoded H-2K antigens but does not express K-region encoded H-2K alloantigens. It also expresses on its cell membrane, H-2 specificities of foreign haplotypes not present on normal AKR lymphoid cells. The molecular basis of the H-2Dd specificity on K36 (H-2k) was analysed by immunoprecipitation and polyacrylamide gel electrophoresis. The specificity was shown to be present on a glycoprotein of apparent molecular weight 45,000. However, antisera against the H-2Dd private specificity (H-2.4) precipitate additional glycoprotein of 45,000D and also 70,000D. In tryptic peptide maps of the isolated 45,000D fraction precipitated by anti-H-2.4 serum from radiolabelled K36 glycoprotein, all H-2Dd specific peptides were present in the same quantitative ratio. This is consistent with the structural identity of the foreign H-2Dd from the K36 tumour with normal H-2Dd and supports the hypothesis of a regulator system controlling the H-2 allelism. Under certain circumstances such a system could cause suppression of one and derepression of the other H-2 gene products.